It'll likely be a bottleneck but since you're coming from onboard graphics (as I remember you stating in your last thread) I wouldn't worry much about that.

The GTX 550ti and AMD 6850 are great cards, but they're not top of the line either. You have to understand that some games are CPU intensive, others are GPU intensive. It also depends what resolution you're using, the lower the resolution, the more CPU will be used to determine your max frame rates, the higher the resolution the more the GPU will determine it. There's so many different games that have different variables and factors of their own that its at the point of you're always going to have a bottleneck somewhere.

So basically your weakest link here for the system would be your CPU, naturally.

Something you can do to research what your system performance will be like is look at benchmarks online. A website I commonly use is Andantech.com as they have a lot of different CPU's and GPU's benchmarks in which you can compare and cross reference.

For example, here is your CPU (this cpu is actually 500mhz faster than yours, but same cpu i believe just higher clock) vs arguably the best current mainstream gaming CPU, the i5-2500k (at stock clocks, can be OC'd on air to up to 4.5 with decent heatsink)

Now as you see, in some games the i5-2500k performs more than double the performance while in other games there's maybe only a 30% difference.

Now we'll look at the graphic cards, the GTX 550TI vs the AMD 6850. Here we'll figure out what the average frame rates were on the same games referenced in the previous benchmark, then cross reference and compare.

Running at 1440x900, your CPU will likely be your bottleneck in majority of games, but if they're playable does the bottleneck really matter? Basically you just want to have a good "balance" in your system, now if you had a Pentium 4 1 core processor and asked if there was a bottleneck, then the obvious answer would be "Yes". That would be a technical bottleneck by any standards, it would always be the limiting factor no matter what game you played. Your CPU on the other hand, should be capable of playing majority of games although upgrading your CPU to the current generation of processors as the benchmark above showed, would yield significant gains.

I can't promise that your CPU will perform great with current gen games, but it wouldn't hurt to pick up a new PSU and graphics card and give it a try. If the performance isn't on par to your expectations, then you can always go from there and upgrade other parts of your system (like your CPU, Motherboard and Ram) as you see fit.